ABSTRACT The on-going Arecibo Pulsar-ALFA (PALFA) survey began in 2004 and is searching for radio pulsars in the Galactic plane at 1.4 GHz. Here we present a comprehensive description of one of its ...main data reduction pipelines that is based on the PRESTO software and includes new interference-excision algorithms and candidate selection heuristics. This pipeline has been used to discover 40 pulsars, bringing the survey's discovery total to 144 pulsars. Of the new discoveries, eight are millisecond pulsars (MSPs; ms) and one is a Fast Radio Burst (FRB). This pipeline has also re-detected 188 previously known pulsars, 60 of them previously discovered by the other PALFA pipelines. We present a novel method for determining the survey sensitivity that accurately takes into account the effects of interference and red noise: we inject synthetic pulsar signals with various parameters into real survey observations and then attempt to recover them with our pipeline. We find that the PALFA survey achieves the sensitivity to MSPs predicted by theoretical models but suffers a degradation for ms that gradually becomes up to ∼10 times worse for at pc cm−3. We estimate 33 3% of the slower pulsars are missed, largely due to red noise. A population synthesis analysis using the sensitivity limits we measured suggests the PALFA survey should have found 224 16 un-recycled pulsars in the data set analyzed, in agreement with the 241 actually detected. The reduced sensitivity could have implications on estimates of the number of long-period pulsars in the Galaxy.
To understand the molecular origins of diseases caused by ultraviolet and visible light, and also to develop photodynamic therapy, it is important to resolve the mechanism of photoinduced DNA damage. ...Damage to DNA bound to a photosensitizer molecule frequently proceeds by one-electron photo-oxidation of guanine, but the precise dynamics of this process are sensitive to the location and the orientation of the photosensitizer, which are very difficult to define in solution. To overcome this, ultrafast time-resolved infrared (TRIR) spectroscopy was performed on photoexcited ruthenium polypyridyl-DNA crystals, the atomic structure of which was determined by X-ray crystallography. By combining the X-ray and TRIR data we are able to define both the geometry of the reaction site and the rates of individual steps in a reversible photoinduced electron-transfer process. This allows us to propose an individual guanine as the reaction site and, intriguingly, reveals that the dynamics in the crystal state are quite similar to those observed in the solvent medium.
Targeting multiple malignancy features such as angiogenesis, proliferation and metastasis with one molecule is an effective strategy in developing potent anticancer agents. Ruthenium metal ...complexation to bioactive scaffolds is reported to enhance their biological activities. Herein, we evaluate the impact of Ru chelation on the pharmacological activities of two bioactive flavones (
1
and
2
) as anticancer candidates. The novel Ru complexes (
1Ru
and
2Ru
) caused a loss of their parent molecules' antiangiogenic activities in an endothelial cell tube formation assay.
1Ru
enhanced the antiproliferative and antimigratory activities of its 4-oxoflavone
1
on MCF-7 breast cancer cells (IC
50
= 66.15 ± 5 μM and 50% migration inhibition,
p
< 0.01 at 1 μM).
2Ru
diminished 4-thioflavone's (
2
) cytotoxic activity on MCF-7 and MDA-MB-231 yet significantly enhanced
2
's migration inhibition (
p
< 0.05) particularly on the MDA-MB-231 cell line. The test derivatives also showed non-intercalative interaction with VEGF and c-myc i-motif DNA sequences.
Targeting multiple malignancy features such as angiogenesis, proliferation and metastasis with one molecule is an effective strategy in developing potent anticancer agents.
Summary
One in four doctors in training in the UK reports feeling ‘burnt out’ due to their work and similar figures are reported in other countries. This two‐group non‐blinded randomised controlled ...trial aimed to determine if a novel text message intervention could reduce burnout and increase well‐being in UK trainee anaesthetists. A total of 279 trainee anaesthetists (Core Training Year 2, Specialty Training Years 3 or 4) were included. All participants received one initial message sharing support resources. The intervention group (139 trainees) received 22 fortnightly text messages over approximately 10 months. Messages drew on 11 evidence‐based themes including: gratitude; social support; self‐efficacy; and self‐compassion. Primary outcomes were burnout (Copenhagen Burnout Inventory) and well‐being (Short Warwick‐Edinburgh Mental Well‐being Scale). Secondary outcomes were as follows: meaning in work; professional value; sickness absence; and consideration of career break. Outcomes were measured via online surveys. Measures of factors that may have affected well‐being were included post‐hoc, including the impact of COVID‐19 (the first UK wave of which coincided with the second half of the trial). The final survey was completed by 153 trainees (74 in the intervention and 79 in the control groups). There were no significant group differences in: burnout (β = ‐1.82, 95%CI ‐6.54–2.91, p = 0.45); well‐being (‐0.52, ‐1.73–0.69, p = 0.40); meaning (‐0.09, ‐0.67–0.50, p = 0.77); value (‐0.01, ‐0.67–0.66, p = 0.99); sick days (0.88, ‐2.08–3.83, p = 0.56); or consideration of career break (OR = 0.44, ‐0.30–1.18, p = 0.24). Exploratory post‐hoc analysis found the intervention was associated with reduced burnout in participants reporting personal or work‐related difficulties during the trial period (‐9.56, ‐17.35 to ‐1.77, p = 0.02) and in participants reporting that the COVID‐19 pandemic had a big negative impact on their well‐being (‐10.38, ‐20.57 to ‐0.19, p = 0.05). Overall, this trial found the intervention had no impact. However, given this intervention is low cost and requires minimal time commitment from recipients, it may warrant adaptation and further evaluation.
We present a new single-pulse pipeline for the PALFA survey to efficiently identify single radio pulses from pulsars, rotating radio transients (RRATs), and fast radio bursts (FRBs). We conducted a ...sensitivity analysis of this new pipeline in which many single pulses were injected into PALFA data and run through the pipeline. We find that for single pulse widths <5 ms, the sensitivity of our new pipeline is at most a factor of ∼2 less sensitive than theoretically predicted. For pulse widths >10 ms, as the DM decreases, the degradation in sensitivity gets worse and can increase up to a factor of ∼4.5. Using this pipeline, we have discovered seven pulsars and two RRATs, and identified three candidate RRATs and one candidate FRB. The confirmed pulsars and RRATs have DMs ranging from 133 to 386 pc cm−3 and flux densities ranging from 20 to 160 mJy. The pulsar periods range from 0.4 to 2.1 s. We report on candidate FRB 141113, which is likely astrophysical and extragalactic, having DM 400 pc cm−3, which is over the Galactic maximum along this line of sight by ∼100-200 pc cm−3. We consider implications for the FRB population and show via simulations that if FRB 141113 is real and extragalactic, the slope of the distribution of integral source counts as a function of flux density (N(>S) ∝ S− ) is 1.4 0.5 (95% confidence range). However, this conclusion is dependent on assumptions that require verification.
We perform a search for continuous gravitational waves from individual supermassive black hole binaries using robust frequentist and Bayesian techniques. We augment standard pulsar timing models with ...the addition of time-variable dispersion measure and frequency variable pulse shape terms. We apply our techniques to the Five Year Data Release from the North American Nanohertz Observatory for Gravitational Waves. We find that there is no evidence for the presence of a detectable continuous gravitational wave; however, we can use these data to place the most constraining upper limits to date on the strength of such gravitational waves. Using the full 17 pulsar data set we place a 95% upper limit on the strain amplitude of h {sub 0} ≲ 3.0 × 10{sup –14} at a frequency of 10 nHz. Furthermore, we place 95% sky-averaged lower limits on the luminosity distance to such gravitational wave sources, finding that d{sub L} ≳ 425 Mpc for sources at a frequency of 10 nHz and chirp mass 10{sup 10} M {sub ☉}. We find that for gravitational wave sources near our best timed pulsars in the sky, the sensitivity of the pulsar timing array is increased by a factor of ∼four over the sky-averaged sensitivity. Finally we place limits on the coalescence rate of the most massive supermassive black hole binaries.
In the modern era of big data, many fields of astronomy are generating huge volumes of data, the analysis of which can sometimes be the limiting factor in research. In this paper, we present a novel ...artificial intelligence (AI) program that identifies pulsars from recent surveys by using image pattern recognition with deep neural nets-the PICS (Pulsar Image-based Classification System) AI. The AI mimics human experts and distinguishes pulsars from noise and interference by looking for patterns from candidate plots. Different from other pulsar selection programs that search for expected patterns, the PICS AI is taught the salient features of different pulsars from a set of human-labeled candidates through machine learning. The training candidates are collected from the Pulsar Arecibo L-band Feed Array (PALFA) survey. The performance of this system can be improved over time as more training data are accumulated. This AI system has been integrated into the PALFA survey pipeline and has discovered six new pulsars to date.
Understanding and improving the behavior of interfaces is essential to the development of safer and high performance Li-based batteries regardless of their range of applications. Indirect methods ...such as impedance spectroscopy or direct methods such as the live in situ observation of batteries cycled within a scanning electron microscope (in situ SEM) are used to determine the interface microstructure/composition evolution upon cycling. These methods are used to establish a direct link between interface properties and batteries performance; they also enable us to spot local interface defects that are crucial to the development of 2D solid-state microbattery, for instance. Indeed, this technology is of interest in powering the new generation of microelectromechanical systems (MEMS). Here, we demonstrate the first ex situ TEM observation of “nanobatteries” obtained by cross-sectioning a microbattery using focus ion beam (FIB) in a dual beam SEM. Then, TEM analyses between pristine, cycled, and faulted all solid-state LiCoO2/solid electrolyte/SnO Li-ion batteries have revealed drastic changes such as the presence, depending on the battery fabrication process, of both cavities within the solid electrolyte layers and low wetting points between the electrolyte and the negative electrode. Moreover, post-mortem TEM observations of cycled microbatteries have revealed a rapid deterioration of the interface upon cycling because of the migration of the chemical elements between stacked layers. Such findings are involved both in the improvement of the reliability of the 2D all solid-state battery assembling process and in the enhancement of their cycling performances. Such achievements constitute the technical platform for our future targets namely the development of live in situ TEM observation of “nanobatteries” cycled within the microscope.
Abstract
We present new discoveries and results from long-term timing of 72 pulsars discovered in the Pulsar Arecibo
L
-band Feed Array (PALFA) survey, including precise determination of astrometric ...and spin parameters, and flux density and scatter broadening measurements at 1.4 GHz. Notable discoveries include two young pulsars (characteristic ages ∼30 kyr) with no apparent supernova remnant associations, three mode-changing, 12 nulling and two intermittent pulsars. We detected eight glitches in five pulsars. Among them is PSR J1939+2609, an apparently old pulsar (characteristic age ∼1 Gy), and PSR J1954+2529, which likely belongs to a newly emerging class of binary pulsars. The latter is the only pulsar among the 72 that is clearly not isolated: a nonrecycled neutron star with a 931 ms spin period in an eccentric (
e
= 0.114) wide (
P
b
= 82.7 days) orbit with a companion of undetermined nature having a minimum mass of ∼0.6
M
⊙
. Since operations at Arecibo ceased in 2020 August, we give a final tally of PALFA sky coverage, and compare its 207 pulsar discoveries to the known population. On average, they are 50% more distant than other Galactic plane radio pulsars; PALFA millisecond pulsars (MSPs) have twice the dispersion measure per unit spin period than the known population of MSP in the plane. The four intermittent pulsars discovered by PALFA more than double the population of such objects, which should help to improve our understanding of pulsar magnetosphere physics. The statistics for these, rotating radio transients, and nulling pulsars suggest that there are many more of these objects in the Galaxy than was previously thought.
Hydration-dependent DNA deformation has been known since Rosalind Franklin recognized that the relative humidity of the sample had to be maintained to observe a single conformation in DNA fiber ...diffraction. We now report for the first time the crystal structure, at the atomic level, of a dehydrated form of a DNA duplex and demonstrate the reversible interconversion to the hydrated form at room temperature. This system, containing d(TCGGCGCCGA) in the presence of Λ-Ru(TAP)2(dppz)2+ (TAP = 1,4,5,8-tetraazaphenanthrene, dppz = dipyrido3,2-a:2′,3′-cphenazine), undergoes a partial transition from an A/B hybrid to the A-DNA conformation, at 84–79% relative humidity. This is accompanied by an increase in kink at the central step from 22° to 51°, with a large movement of the terminal bases forming the intercalation site. This transition is reversible on rehydration. Seven data sets, collected from one crystal at room temperature, show the consequences of dehydration at near-atomic resolution. This result highlights that crystals, traditionally thought of as static systems, are still dynamic and therefore can be the subject of further experimentation.
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